1. Field of the Invention
The invention relates to an amplifier circuit for amplifying a high-frequency input signal.
2. Description of the Background Art
Amplifier circuits for amplifying a high-frequency input signal, as is generated, for example, in wireless data transmission from a receiver antenna, frequently comprise an amplifier stage, which amplifies the high-frequency input signal as a function of an operating point of the amplifier stage.
An undesirable property of conventional amplifier stages is that their operating point depends on a level of the high-frequency input signal. The cause of this, for example, may be that an average base-emitter current of an amplifier stage bipolar transistor, wired as an amplifier, increases with an increasing level of the high-frequency input signal; as a result, the operating point of the bipolar transistors shifts and an available output voltage swing is reduced.